Arc discharge control device



Jan. 7, 1941. w, HANSELL 2,227,829

ARC DISCHARGE CONTROL DEVICE Filed Jan. 7, 1938 8 Sheets-Sheet l l MM H ll60- x We U25 im INVENTOR.

W HANSELL BY 7d@ A TTORNEY.

Jan. 7, 1941.

c. w. HANSELL 2,227,829

ARC DISCHARGE CONTROL DEVICE 8 Sheets-Sheet 2 Filed Jan. 7, 1958 INVENTOR, C. nf. HA NSELL BY v A TTORNEY.

Jan. 7, 1941. c, w HANsELL ARC DISCHARGE; CONTROL DEVICE 8 Sheets-Sheet 3 Filed Jan. 7, 1958 nvvENToR. W HANSELL BY l ATTORNEY.

Jan. 7, 1941. c. w. HANsELL ARC DISCHARGE CONTROL DEVICE Filed Jan. 7, 19:58

8 Sheets-Sheet 4 w 0 l. D.

A. C, POWER SW/ .l A MM TM U7 w w A m fao w m w m w MHG; mz 35mm.

RPRODl/CBLE Nl//TY RPAODUCA D/.S' CON T/NUI TY SECND NUDE AMPERES .4. C. POWER INVENTOR. C'. W HNSELL ATTORNEY.

Jam 7, 1941- f HANsELL 2,227,829

ARG DISCHARGE CONTROL DEVICE Filed Jan. 7, 1958 8 Sheets-Sheet 5 AC. POWER (/NPUT D. LOAD acPowER /NPUT SOURCE 0F FLUCTUT/ NG D. C. POWER VOLTAGE I NV EN TOR.

ATTORNEY.

Jan, 7, 1941.'

c. w. HANsELL 2,227,829

ARC DISCHARGE CONTROL DEVICE Filed Jan. 7, 19:58 8 Sheets-Sheet 6 4 56 RELAY mm3/T /26\ j fgf 55 21 l-illll ,l f l 03N o. c. ,Z5 ac. POWER 0,40 sou/Q05 L o- A.c. /GN/T/ON POWER INPUT P n0 ul@ 60 J4 0. c. ourPz/ T gummi/2li E {.99 sw/TcH AND Acc/ncu/T c BREAKER L T AUX/MARY REC'T/F/ER ,23 INVEN TOR.

C W HANSELL ATTORNEY.

Jan. 7, 1941. c. w. HANsELL. 2,227,829 Anc DIscHARGn CONTROL DEVICE Filed Jan. '7, 1958 8 sheets-sheet 7 INVEN TOR. c. w. HANsELL ATTORNEY.

Jan. 7, 1941. c. w. HANsELL ARC DISCHARGE CONTROL DEVICE Filed Jan. 7, 1938 8 Sheets-Sheet 8 m 0 L D.

AL'. POWR INVENTOR. Z. W HANSELL )i /wf/LM/ ATTORNEY.

d W n i.. W2 .HHHLM W PatentedX Jan. 7, 1941 witze,

fearsome-commun@ Clarence W. Port .lend-son, N. Y., assignon otAmerica, acorporai 'orto Radio Corporati tion of annealed y.mmvlllry "l, lsaaseral No. ll'iztg'llu'` 'Y faz calmallol. '11s-e363) e Y This inventionrelates to` electr'lcalk dis-y charges in low pressure gasesand vapors and has for itsobjectfthe provision ofjdevices suitable fort useasrelays, rswtches, controllers,,regulators and 5 limitersofelectric current. ,It may,be,.=used inv 1 v eonneetlon wimy both dlrect and alternatingk cur-fa rent but isparticularlyy adaptedorfuse in direct v e, rnave round that Lthe voltage) drab ybetween anode` and cathodefis increased by thepresence of each barre-ieny Furthermore, over a large `range yof currents. the` total voltagebetween-any one ycurrent circuits.r Theinvention is` based.y uporlgy f, studies and experiments with:` yelectrlealvv disl chargesv through holes in barriers between chaxn-` bersecontaining Agas or vapor at lowy pressure. rIg

barrier and the kcathode remains-almost constant regardlessoi current ow in the arc and in spte 7of additional current which may `bepassed between-,thefbarriver andthe cathode from some 'external supply. `1n other, words, over a large range of currents. I may pass any amount of cur- 10 rent from any one of the barriers to the cathode Bln' parallel wlth, andln tneseme direction as, the

lanode ai'cl withoutproducing much, vitam',

' change in the/voltages from the various barriers properties in my present invention.l This disf coverywas. made asa result otlmyrown'mexperiments y ofthe V e t #2,022,465,.#2,063,249 andy #2,063,250 .and other conducted with electrical vacuum pumps holes and orices.

Accordingjto' myinvention two'low pressure devices involvinvgxelectrical `discharges lthrough general type .deser'ibedlrr my S.1Patents l and the-anode to the cathode. Thisconditionof nearly constant voltage distribution between barvtiers, anode yand cathode holds over-av very large range' ofy positive current values.V I- have also found thattheveltage distribution yarid yeltage or vapor filled ,chambers are separated from one y another by a metal barrier with a holein it', one.

andthe other Withva :athode the metal: barrier',y or firs@anodt,"there` may also be established. discharge btwn thecathode andk thelsecond anpdethrou'gh `,the helfe ln the barrier.

the barrier,

pressure arc discharge phenomenal" Il 'the cathf have allow value ofA rotem volts, upon the dimensions or the'deviceand/to some extentg] llponfth'vlior pressure; `.'Ifhefvalue of voltage "40 of current.vr Irl` practice, the voltage dropwill ofthese chambers 'beingpr'ovided with an anode' l Then. iflan arc discharge` is established t between the cathode and values areremarkablyindependentof the gas or 20 vapordensity inthe path ofthe arc and substantially l unaiected by the Y pressure variations of a.

degreekcommon in mercury arc dischargedevices.

e Howevenl have also` found that if Icontinue to 4`increase thevcurrent inaportion oi' the, arc which 25 through ahole in a. barrier then, at ia. critilfoalfvalueof current, the voltagedrop inthe arc e increases almost abruptly and usually, anv oscillationv or `fluctuation of current sets in which causes the current tol I iowintermittently instead of 30 The discharge between the cathode and.u A ywhicl'l[maybe considereditojbe a conf-.N mmol-15 0.? holdmg PIC exhibits .the *usual 10W y.barrier 'and uponthegas'` or vapor pressure. It ,l l .l seems to be ro rtional tothe asorvva r re- Lode is a mercurypool, forexample. ,thevoltage p po g po p s drop between the ball'l'iex"y andltheocathode will,

drop remains substantiallyconstant `'regar'iless o( y, y the currentf in the arc over fa' tremendous 'range' usually change very little overa rafrlgeof. cul-rent` as great as 1000 toil'. j 45 l"The" arycsifroni` the `secolfld' lanode toY the catthotie through the hole inr the barrier, orfirst anode, fj also exhibitsa 'nearly constant; arc for low] y'values'oficurrerltbut this'voltagedropls con-1i; v v e vfsiderably greaterth'an that'bet'we'en thebarrier and the' cathode. Inpracticehave" usually yfoun`d`-that the passage of the are through lr'smallA u hele ,ln t the steel barrier increases 4thevoltage drop for low' values or currenty liyabout,y '20 f volts. o, By "placingfadditional apertredbarriers, or j barrier vanodes, in the'path'ofthe arctoah an'-v steadily. The criticalvalue of current is dependent upon the shape and sizeof the hole in the sure and increases rapidly witl'liy increase in the 'and a conical hole in 1a' l inchv steel plategf'havng 40 alminimurriv diameterof oflan inch, limiting hasbeen producedrat current values ranging from "about 2 i ampres l t'20' ari'iperes, depending `upon v'the vapor pressure and density. -The vapor pres- 'f sure and density in turn',` usually dependent 'i almostaltogetherupon the temperature of the coolestpart o! `th"evacated` chamber containing f rt wlllfbefetedtllettheare discharge through 5o fthe hole j eithibits nearly Aconstant *low D." C. voltage drop'fover all-values V'olf current' upto nearly 'the limitingl value and then', forv theflimiting valueof` "currenuexhibits nearlyl c zonst'antl average or-D50.' current for all value'y of voltageup to the 53 breakdown voltage of the device and its insulation.

Inorderthatothersskilledintheartmaybe given sumcient information to practice my invention, several speciilc examples are illustrated in the drawings and will now be described.

Intheaccomllnyingdrawings.l"ls.lisa erom-sectional view of a device employing the features and particulars o! my invention: Fig. 2 isawiringdiagramofthedeviceandconnections therefor; Pig. 3 illustrates a modlilcation wherein a magnetic ileld coil is employed to produce additional eilects and also illustrates a modified form of tlrst anode structure; Fig. 4 is a crosssectional view of a further modiilcation of my invention which is somewhat more compact; Figs.5,6and8to11showwirlngdiagramsior utilizing the device shown in Figs. 3 and 4; Fig. 7 is a graph explanatory of my present invention; Fig. 12 illustrates diagrammatically a further modification of my invention, particularly desirable where several values of iixed voltages are desired; Fig. 13 shows diagrammatically a iurther modicaon of my device and its associated wiring diagram; Hg. 14 shows still another modiication of my invention employing a duid cooled electrode and plurality of second anodes to be used for a full-wave rectier; Fig. 15 is a crosssectional view of another modiilcation oi my invention particularly suited to push-pull or fullwave operation; Fig. 16 shows a wiring diagram for my device utilizing a plurality oi magnetizing coils connected in bucking relation; Fig, 17 illustrates the behavior of the mercury arc in my invention under various conditions.

Referring to Fig. 1, which is a drawing of a particular arrangement which I have used, there is shown an outer envelope I which is obtained by altering a standard 4 inch steel pipe cross. This pipe cross has four openings. Over one oi the openings is iitted a blank plate 3 held in place by bolts 5, and over the diametrically opposite opening is iitted a high temperaturev glass or quartz plate `I held in place by steel ilange 9 and bolts I|. Over the lower opening is fitted an assembly including insulators i3 and 25, steel ring I5 and steel ilange I9, all held tightly in place by insulated bolts 2i. An additional plate 23 is provided to serve as a mounting plate and is attached to plate I! by bolts 25. Over the upper opening is provided insulator 21, a steel ring 29, a second insulator 3| and a ilange 33, held tightly in place by bolts 35, which are accurately iltted together and joined by means of gasketsofthinvarnishedsilhthusmakinga hermetically sealed container.

'I'he container is evacuated through connection 3S, a water cooled condenser trap li, connection and vacuum pump II. A mercury vacuum gauge I3 is connected to connection 45.

Held in a depression in iiange Il is a mercury pool 49 to serve as a cathode. Standing in this pool of mercury is a short cylinder oi high temperature glass, the function of which is to restrict the arc to the area of the mercury surface within the cylinder. Connected with ring i5 is an arc starter point 53 made of a carborundum compound commonly known as 'Ihyrite. This point is mounted so that its tip is within about l. ofaninchiromthesurface ofthemercury.

Mmmtedonsteelringliisailrstanode 55 consisting of a steel cylinder closed at the lower endwithasteelplate 55a. Throughthesteel plate is a hole 51. llounted on steel flange 33 is a cylindrical second anode 5l, the end of which ananas is located immediately over hole Il. 'Die second anodeisdrilledattheendasshownatll. The depthoi'tbisdrilledhollowmaybevariedls desired. Theiunction oithishollowistodlstribute the power losses at the second anode over a larger area and control thebehavior ot the arc.

Fig.2sbowsaachematiediagramoitheessen tial elements used in the power and control circuits for demonstrating my inventim. A. D. C. generator III supplies power through a switch |33 and a current limiting resistance |35 to iirst anode 55. A second D. C. generator |31 suwlies power through switch III, variable resistance III and reactance or choke Iil and load reactance I|3 to the second anode 53. A large condenser II5 and a surge arrester III are used to keep high frequency and transient currents out oi the generator circuit. A load resistance consisting of incandescent lamps |2I is connected across reactor |I3.

For starting the arc, a transformer |23 is provided which is supplied with cycle, 110 volt A. C. power through push button switch |25. The transformer, which is of the type commonly employed in oil heating plants for electric ignition, develops an open circuit A. C. voltage oi about 15,000 volts but is designed to have a high leakage reactance and secondary resistance so that secondary current is always limited to a low value. A transformer for neon lamp excitation has similar characteristics and could as well be used. 'Ihe secondary winding ot the transformer is connected between steel iiange I3 ci Fig. l and steel ring I5 and through these applies the 15,000 volts starting potential across the small gap between the starter point 53 and mercury pool 40 within the isolating cylinder 5I By applying potential to iirst anode 55 and then momentarily energizing transformer |23 by closing switch |25, it is possibleto start an arc betwem the iirst anode and the mercury path. This arc will continue indefinitely and is the means for maintaining continuous ionimtion in the chamber between the first anode and cathode.

By closing switch |09 a current can be drawn through the hole 5'I to the second anode 53. This current can be varied at will by varying the value of resistance III and the voltage of generator |01 from 'a value oi a few milliamperes up to a critical limiting value ranging from l to 50 amperes in one particular case, depending upon dimensions oi the hole 51 and the gas or vapor pressure in the vicinity oi the hole.

Alter the critical or limiting value oi current is reached any further attempt to increase the current results substantially in only increasing the voltage drop between the mercury pool cathode and the second anode. Fig. 'I is a typical current versus voltage characteristic of a mercury arc through a hole, measured with the arc discharge device and circuits illustrated in Figs. 1 and 2- 'I'he hole in the iirst or barrier anode Was-tapered, with a inch minimum diameter at the end nearest the second anode. 'Ihe cup in the second anode was 1 inch in diameter and l inch deep. 'Ihe smallincrease in current with increasing voltage alter limiting in Fig. 'I is believed to be due to increasing vapor pressure, taking place during measurement, rather than to an inherent characteristic oi' the arc. At any rate, other measured characteristics have given both slightly increasing and slightly decreasing current with increasing voltage after limiting.

I have found that, i! the average or D. C. voltage drop exceeds about 50 or 60 volts, the cur- I rent through the hole in the barrier anode to the second anode oscillates or is subject to intermittent interruption. In the presence of a holding arc to the barrier anode continuous oscillations in second anode current may take place during current limiting. In the absence of a holding arc the first interruption or oscillation of second anode current interrupts the arc permanently unless the arc is restarted. Such an arrangement, in series with a'power circuit, will act as a quick break instantaneous circuit breaker to interrupt anyV current which reaches the limiting value.

I have also found that if I place a coil of wire around the arc discharge device shown in Fig. l and energize the coil with direct current in such a way as to set up a magnetic eld approximately parallel to the arc path from the cathode, through the hole to the anode, I can produce a very pronounced but controllable lowering of the value of current which causes limiting and if the magnetic field is strong enough, I can interrupt the anode current by means of the magnetic eld. So far as I know, this is the first case on record where a mercury arc current, at ordinary pressure, has been controlled by means of a magnetic field. Since the strength of field required was quite moderate I believe the magnetic field control of an arc, n

which I have found, as well as the circuit interrupting properties of arcs through holes, without a magnetic field, may have very important practical applications.

Fig- 3 shows a modification of the device and circuits of Figs. 1 and 2 in which a magnetic eld coil 65, and the source of controllable current 61 for energizing it is added. The electrodes are shortened to facilitate observation of the arc through the high temperature glass window in one arm of the cross-shaped vessel. The barrier or first anode is insulated by means of a glass tubing slipped over it and a ring-shaped glass plate 6l placed over the end, so that the arc to the first or barrier anode is forced to terminate near the hole. An insulated steel arc deflector 'Il is also suspended upon insulated posts 59 under the hole in the barrier electrode as shown. With this arrangement the arc from both anodes to the mercury pool cathode is forced to travel over a radial path near the hole in a region where an intense magnetic eld can be produced. With this arrangement the'v anode current can be cut off much more easily and held cut off more easily than without the deilector. I was able to cut on and olf an anode current of as much as 40 amperes from a 400 volt'l source with this arrangement with a moderately strong magnetic field. As a further modification of this figure, a 11.; inch hole may be drilled in the center of the steel deflector plate 1I to allow a small stream of electrons to shoot up through the hole in the defiector and the cathanode. The small stream of electrons keeps ionization alive near the anode and makes it much more diicult to hold the anode current cut olf. Without this hole, after the anode cuts olf, it stays cut off until the arc tor thesteel plate expands over the edge of the plate.

When the anode current is cut oif the small stream or pencil of electrons passing through the g inch hole` in the steel plate, and up through the cathanode hole, is clearly visible.

With this and similar arrangements al1 of the phenomena described here in connection with arcs through holes and with the whirling arc have been demonstrated and the behavior of the arc has been observed directly.

I have found that the voltage drop between a cathode and the barrier is substantially unaffected by the magnetic neld which, I believe, is in accordance with the common experience. It might also be assumed that a magnetic field parallel to the arc path through the hole in the barrier should have no effect upon the voltage drop through the arc since a current parallel to the magnetic field made up of electrons and ions moving parallel to the field would not be influenced by the eld. The observed strong influence upon the arc, therefore, requires explanationy In observing arcs through holes and barriers, I have noted that on the cathode side of the barrier the arc seems to be in the form of a white cone or flame having the apex of the cone in the hole in the barrier. Applying a magnetic field spreads out the base of the cone and, applying a stronger field, often makes it suddenly flatten out into a disc near the barrier and extinguish itself. There must, therefore, be a converging of current toward the hole so that there is a considerable radial component of current owing from outsideA toward the axis of the arc, or vice versa, depending upon the conception of direction of current flow. (The conventional assumption of current iiow is contrary to the physical motion of electrons constituting the bulk of the current.) This radial component of current flows at right angles to the magnetic field and the electrons and ions constituting the current are deflected by the field in a direction at right angles to their normal path. As a result the magnetic field tends to whirl the electrons and ions around the axis. Molecules present in the space are also carried around in the whirling motion and this results in `a 1ow pressure whirlwind centering on the axis of the arc and ending at the hole in the cathanode. This has several effects as follows:

1. The whirling electrons are thrown away from the axis of the tube by centrifugal force and the force of the magnetic field and, when the field is strong, only a few electrons travelling the whole distance from cathode along the axis of the tube can reach the hole in the cathanode. This phenomena is somewhat analogous to the whirlpool in the drain hole of a bath tube When water is being drained from the tub. It is a common observation that the whirling, through centrifugal force, slows up the rate of flow through the drain.

2. 'I'he whirling ions and molecules also are thrown away from the axis of the tube by centrifugal force and a relatively high vacuum is created along the axis of the tube and at the cathanode hole. Reduction of ionization near the hole resulting from the decreased pressure prevents neutralization of space charge drop near the hole and substantially reduces or prevents electron current to the hole and the anode.

3. The spiral path followed by the electrons in travelling toward the hole in the cathanode and the slowing up of radial velocity due to the magnetic field greatly increases the electron space charge in the vicinity of the hole and this causes a high space chargevoltage drop in the current to the anode.

4. In one form of tube used the cathode hole is in the form of a relatively long but narrow slot. Electrons approaching the hole are necessarily possessed of a considerable component of velocity at right angles to the normal arc path and conuitk sequently tend to strike the walls of the slot instead of passing through to the anode.

5. The whirling gas acts like any other rotating conductor in a magnetic iield and produces a counter electromotive force due to the rotation which tends to reduce or stop the current. In the complete absence of friction (an impossible case in a practical instance) the velocity of rotation of the whirling gas is limited only by the velocity needed to produce an electro-motive force equal to the applied voltage. In a practical case high velocities of rotation may be expected. In general, the velocities of rotation would be roughly inversely proportional to the degree of ionization and proportional to the square o! the voltage gradient or voltage drop in the whirling portion of the arc.

In the presence of a holding arc to a barrier, unless the field is made very strong, the arc, through the hole, after being extinguished. restrikes through the hole and the whole process is repeated over and over again. If the holding arc to the barrier is removed by opening the source of direct current to it before the magnetic field is applied, then the application of a strong magnetic field will extinguish the anode current through the hole and it will remain extinguished permanently until restarted.

These observations of the operation and behavior of the arc, and theory, indicate that there is a radial concentration of current in the arc as we approach the hole from the cathode side. This radial concentration gives us a radial cornponent of current which cuts across the magnetic field and is, therefore, acted upon by forces tending to move the conductor at right angles tothe field. This gives a whirling motion of the vapor around the axis of the arc through the hole. The whirling, due to centrifugal force, reduces the vapor and electron density along the axis of the arc and in the hole. Reduced electron and ion densities require higher velocities for a given current and the higher velocities increase the rate of 'whirling and force the arc to spread out into a broader cone. This, in turn, increases the radial component of current, lowers the electron and ion density near the hole still further and increases the velocity and spread of whirling near the hole. The whole process tends to be regenerative so that, in one design of the device, as the magnetic field is slowly increased, the arc through the hole continues to be relatively unaiected until a critical value of field is reached, at which the whirling suddenly becomes unstable or regenerative and the arc is suddenly extinguished by a scarcity of gas or vapor to maintain ionization in or near the hole. Likewise, I have found that, if the arc is started through the hole and the arc current is kept small, while the magnetic field is on, the arc may continue indefinitely. However, if we increase the urrent in the arc we thereby increase the whirling and eventually, at a critical maximum value of current in a constant magnetic field and with constant vapor pressure, the arc will suddenly extinguish itself. 'Ihe critical value of current depends upon the dimensions of the devict.I the vapor density and strength of the magnetic iield. Assuming a constant temperature or pressure regulated device of fixed dimensions. the critical value of current at which the arc extinguishes itself is dependent only upon the strength of the magnetic field and is substantially inversely proportional to the strength of the field.

One long felt need in connection with all kinds of rectiers, for converting alternating to direct current, is a device for use as a switch and circuit breaker for the direct current outputs of the rectiers. At present neither low voltage, high current nor high voltage low current rectifiers are ordinarily provided with circuit breakers in their direct current output circuits. One reason for this is that direct currents arevery hard to interrupt by means of ordinary circuit beakers. In alternating current applications circuit breakers work fairly well because the current goes through zero twice per cycle and can be prevented from building up again, after going through zero, by providing for rapid deionization. In the case of direct currents the current does not oscillate above and below zero and deionization is far more dlmcult to accomplish. Direct currents may be controlled in a device of the present invention with the magnetic field producing the whirling arc in the manner described.

It will be noted that the regenerative tendency in the whirling of the arc gives the cut-oif of anode current a suddenness and positiveness or snap-action equivalent to the elect sought deliberately in relays, quick break switches, thermostats, etc. It is very desirable in an arc discharge device which might be used as a controlled circuit breaker, automatic overload circuit breaker or equivalent of an instantaneous fuse. The arc in such a device has either a very low resistance or infinite resistance and a rapid transition from one condition to the other. Due to the rapid transition from low resistance to open circuit, the speed of which increases with increasing current. heating of the device is kept small and it can interrupt relatively enormous amounts of power without damage to itself.

In practice, if there is no holding arc to the barrier, the arc to the anode, after extinguishing itself, remains extinguished. I have also found that, with a suitably designed device, if the magnetic field is made strong enough the field can be applied. or increased, to cut of! the anode current and the anode current will remain cut ott even though there is a continuous holding arc to the barrier. To obtain this condition it is necessary that the holding arc, or a portion of it. be made to follow a more or less radial path terminating near the hole in the barrier. This is the purpose of the insulated defiecting discs 61 and H shown in the modification of Fig. 3. Then the holding arc current can produce enough whirling to maintain such low vapor pressure at and near the hole that, once the anode arc is extinguished, it cannot strike through again'. With this arrangement we may start the anode current again at will by reducing momentarily either the magnetic iield or the holding arc current.

I have also found that, with the arrangement just described, I can either start or stop the anode current by setting the magnetic neld at a suitable constant value and then varying the arc current to the barrier. A high barrier arc current will extinguish the anode current and a low barrier current will permit it to strike through again. In some cases, due to the whirling added by the anode current itself, I have found that the anode current can be made to start and stop itself repeatedly. In other cases, where the anode current is not great enough to start and stop itself, a surprisingly small percentage variation in the barrier arc current can be made to control the anode current. In other words, the device thctopsuriaoeofplatelltheaendanodcinsulatllisattachedbymeansoiiiameand screwall. Thesccondanodeisclampedto theinsulatorllbymeansoi'anode. Thisanodeiamaderatherlargeindiametaandiaprovidedwithiinstoincreaseitsheatradiaiingability. Inthismodiiicationthearcdenectis attachedbymeansofaninsulatingbolttoihe lowerplateli. Thearcdeilectorispreierablyof magnedcmateriaLsuchasironorsteelandis coatedwithaporcelainenamelcoating 'llotthesametypeaausedontheiiratanodelt Thestarterelectrodeilishyrod .whichpassesthroughaninsulatoriastmed through a hole in plate 1i. 'nie on showninthetopoithearcdeiiectotandthcinsulation on it serve to reduce losses and heating due to high velocity ions pulled through the hole in the barrier anode. Under some conditions, particularly when the current through the hole totheiirstanodeisbeinginten'upteihombardment of the arc deiiector may be quite severe. The arc deector is not at all essential in connectlon with my invention but it does give a greater sensitiveness or ease of control by restricting the arc path, makingthepathmore nearly radial, intensifying the magnetic iield in thearcrestrictedpathandreducingcirculation of vapor which would tend to prevent establishingahighvacmiminthehole. I

I have not shown the magnetic field coil in Fig. 4 but its presence encircling the axis of the device should be assumed. It should also be `a.s sumed that the electrodes may contain passages for the circulation of a cooling liquid, as shown in submuent iigures, and that the temperature of the liquid may be controlled with a thermostat and radiator o! the type commonly used in automobiles, or of any other suitable type.

Fig. 5 shows one of many possible circuits for using my are discharge device. In this case, it is shown in a circuit for controlling the direct current output of a converter for converting alternating current power into direct current power. This converter may be a rectiiier, a. mo-

`tor generator or rotary converter.

The arrangement shown includes a high voltage transformer |23 and spark gap ignition of the arc with a relay I3! for removing the ignitioncun'entassoonasthearctothebarrier anode is started. However. the ignition current may be left on continuously in a suitably dealmedsysteiniidcdred."lhccurrenttothebar rieranodeilowsthmtharhetatllJoradjtiiigthcvalucoclmenttothe neldedlilthrwghthcarctothecathodcand thmmitthrmmhthcloadandbacktolesour. ihemainanodecurr'entpassesthroughthearc throughtheholeinthebarrieatothecathode, mittotheloadandbacktothesour. Ifthe loadisonewhichmaybecompletelyintcrrupted attimesasmalllcadwrrymtobtainedbyahunty'iligai'ealataneeorsomelocalapparatusacmas currentcanowandnodamageresults. The

whirling arc device vprotects itself from damage even on short circuit because, as pointedout, it has eitheraveryloworveryhigh resistance with rapid transition from one condition to the other so that high average power loss in the device is imposible. connected across the load circuit and series re' actors may be desirable in some cases for smoothingoutpulsingcurrentsintoashortcircuitor low resistance load and for holding down peak currents through the arc.

Inthearrangementofthisgureitispossible, by adjusting the temperature of the arc discharge device and by adjusting the rheostat |05 tocausecurrentlimitingatanydesiredvalueof load current. If, for example, the full load current is 1000 amperes, then the arc discharge devicemaybesettostartlimitingatthisvalueand the power source will be automatically protected from overloads. l,

Fig. 6 is another circuit modification in which the iield coil is connected in series with the main anode and the load. In this arrangement the simultaneous increase in magnetic iield and arc current through the hole with increasing load gives a sharper cut-oil? or limiting adjustment which is less dependent upon temperature and vapor pressure in the device. The reactance of the iield coil also tends to reduce rapid fluctuations in load current.

Fig. 8 is a further modiiication in which the field coil is in series with the connection to the cathode so that it carries all of the load current. It desired. two field coils having diilerent numbers of turns and size oi conductor mightbe used in series with the connections to the two anodes instead of a single coil in the cathode circuit.

Fig. 9 is a modiiication having a vibrator induction coil III for arc starting. In this ai'- rangement, as soon as power is thrown on, the vibrator operates until an arc is started to the barrier anode after which the current to the barrier anode through one coil of the vibrator holds the vibrator contact open. The starter point I, in this case, is mounted directly on the barrier anode. It should preferably be made of a high resistance material such as baked graphite and clay or a carborundum compound, such as "I'hyrite. In this figure the magnetic neld coll is shown in series with the negative return lead of the load. This gives a similar effect to that in the modification shown in Fig. 8 where the field coil is in series with the cathode.

Fig. 10 shows another arrangement for utilizing my arc discharge device as a current limiter and overload circuit breaker. In the arrangement shown, if we close switch |55 to the 110 volts, 60 cycle power supply, the arc is started automatically and power delivered to the load. The relay |51, which is connected in series with the barrier anode, removes the ignition potential as soon as the arc is started. In case of overload or short circuit in the load circuit a relay |59 in the ground or negative return lead operates and energizes iield coil 65 and interrupts the current. Depending upon the type of relay used the interruption may be momentary or permanent. Also relays may be used to give various numbers and spacings of reclosings followed by lockout if the short circuit persists, or by cancellation of timing sequence arrangements if the short circuit is cleared and locked out. Such arrangements are Well known in the power industry. In this arrangement we may use the arc device as a direct current switch by adding manually or remotely operated switches or relays for applying and removing the field coil energization.

Fig. 11 is a further modification in which ignition is applied manually by means of push button switch |25 and the connection to the barrier anode is opened by means of relay |33 as soon as the arc from the anode through the hole is established. The field coil 65 in this modification is connected in series with the second anode supply lead. Resistance and are connected across the iield coil and the relay, respectively, in order to protect them against overvoltage and/or heavy current flow. By adjusting the number of turns in the field coil 65 or by varying the shunt resistance ||0 the tube may be made to limit the load current to any desired value. In the arrangements in this figure an overload or short circuit interrupts the load permanently until the circuit is re-established by applying the ignition power manually.

Fig. l2 shows another arrangement of my device with a plurality of series barriers 55, |63, |61 and |1|, each having a hole therethrough in which an arc may be established. With this arrangement a series of differently regulated power voltages may be obtained. The arrangement may serve as voltage divider, voltage regulator and as a group of condensers of extremely large capacity for bypassing A. C. compounds of load on the various voltage taps. My device gives control of the various voltages through a choice of hole dimensions, as well as choice of gas and electrode material, and is capable o'f handling relatively high power. The resistances iGi, |55, |69 and |13 shown connected in series between theA positive power source and the barrier anodes should preferably be tungsten filaments, such as lamps, operated at a moderate temperature, so that their values of resistance will increase with increasing current and reduce the effect of voltage variations of the power source.

` Fig. 13 shows an alternative form of control device in which two anodes have their currents passed through a hole in a barrier. One of these anodes Il, which may be called a control anode, provides straight path for the arc through the hole. The other anode III. which may be called the controlled anode, requires a curved arc path between itself and the hole to the cathode. In the absence of limiting the arc to the controlled anode ill. has no difficulty in following a curved path in the ionized sas or vapor. However, in the presence of limiting with accompanying low gas or vapor pressure and insumcient ionization the arc cannot follow a curved path readily. Consequently, applying or increasing the current and voltage on the control anode can decrease or cut on' the current from the controlled anode. This action is improved `by the presence of a magnetic field parallel to the axis of the hole, which may be supplied in any of the ways shown in the previous figures.

In this figure I have shown manual arc starting by means oi' push button |25 and manual control oi' relay III by means of the switch |25 for applying or removing the controlled anode current for controlling the operation of the device.'

Fig. 14 illustrates an application of my invention to a single phase full wave rectifier. I have shown a rectifier having a liquid mercury cathode 49, cathode insulator and a spark gap arc starter 53. The rst or barrier anode 55 is provided with water cooling passage |83; the water supplied to the cooling passage should preferably be temperature controlled. The anode mounting plate |90 is insulated from the barrier anode 55 by means of insulator |01. Through apertures in plate |90, anodes |9| and |92 are mounted by means of insulators |89. The anodes are clamped to this insulator by means of nuts |94 and |95. A barrier |93 is provided to isolate the two anodes. A magnetic field coil 55 is provided for establishing an axial magnetic field, more or less parallel to the arc as described in previous modiiicatlons. In the particular circuit shown the field coil is in series with the direct current output circuit of the rectifier to make it serve both as an arc controlling means and as a reactor for a smoothing filter to take out voltage ripples. Power is supplied to the rectifier through transformer 2|| which is connected to the main power line through switch and circuit breaker 205 and disconnect switches 2|. I have shown condensers |99 and |91 across the output circuit on each side of the field coil to further improve the smoothing. In addition, the condenser nearest the rectifier improves the regulation or constancy of output voltage with variation in load by facilitat-ing the flow of high peak currents through the arc. The other condenser may also serve to bypass A. C. components or fluctuations in load current. In this modification I have indicated an auxiliary rectifier 20| for maintaining an arc to the barrier anode and a relay 203 with its coil in series with the connection to the barrier anode for removing the ignition power after the arc is established. This same relay controls operation of the main rectifier switch and circuit breaker so that anode power is applied only while the arc is established to the barrier anode. lThe auxiliary rectifier and ignition transformer are supplied from the main A. C. input lines through disconnect switch 2|5, step-down transformer 209 and control switch 201.* In operation of the device it is only necessary to close the control switch 201 to start up the whole rectifier and to open the same switch to close it down.

The rectifier is self-protected against ovcrloads oozlev support `2|'I which' may be made either 'off and short circuiting in the output because, it the averagek or D. C. current throughl the 4hole mi the brrier and through the neld eollneeomesgtoo high limitingf'sets lin f-automatically 'due tol-the viously'described. r Fig: yi5 shows; in cross current limitingrectiiler in which each of twol main lanodessdraws current through individualy holes in a barriery anode. `In this modiiication the'mercury ipool cathode 48 isfcontained in 'a' depressioninthe base plate 15. The -body ltyis formed of' a :cylinder o! high temperature" glass such as Pyrex." The ilrst or barrier anodes 1f 225 are clamped by screws 225`to the barrier anmetal, such as steel, or roi insulating material. The barrier anode support 2I1 and. base plate 15 are clamped together by means of screws 22|` To the which screw into insulator 'postsj'2`I/9. barrier anode structures are clamped anodesupports 221 bylmeans* of clamping rings v229` 'and screws 230. These anode'supports',each of which are in the shape ofl a hollow cone of insulating material, such 'as' porcelain, have` the anodes 225.1 clamped thereto by bolts passing through the' small end.l The Abarrier anodes 225y are shown supplied with'water cooling passages 224 for theV purpose described in the descriptio'nof'Fig. 14.

. 1n thlsmcdlncatio'nif the holes in the barrlerkgj anodes 223 have asuitable size and the tem# perature and pressure of gas or vapor'aregprop erly controlled,such as by meansof the water f passages shown, this rectifier is self-protected by virtue of simple limiting" of the type indicated in Figf'l, although, if desired, amagnetic vfield may also be used toassi'st -i'n controlling the limdevice shown in thisilgure is used for a rectifier it may also beused asa push-pull type oi' oscil-'y lator for converting direct `current into high ire-- quency alternatingl current' power.v

Fig.'r 16 shows a modification of Fig.` 6 employ-- ing` two neld -coils for producing a magneticeld Y parallel to the `axis of theelectrodes and the arc. Each of these coils areso'ldesigned that'the'knormal vmaximum Lcurrent is much larger thanv necessary to" cut oif @theanode` current. "As 'f shown in thefigure,` the anode to cathode path'in the whirling arc tube is connected in series with the direct'currenty outputleads of rectifier i'3l limit the'loady current to'-10 amperes, or less.

Assuming, ,nounl thatv the rectier kis `operat ing the series yfield coil- 651will then ls1`1bstantially`- prevent thevfiow ofIload currentlflnorder to permit the normal loadvcurreni'.'l to iio'w asecond field coil 66 is providedlwhich-'ls energi'aed'fro'm` an auxiliary rectifier" 20|. .This field coil is'energized in a direction to oppose the magnetic iield oi the tlrst coil.' The `higher the'current israised in the ioppo'sing iield vthe higher will be the lloady current drawn' from tHeY-rectifier up-to a point where the'currentis' limited `substantially only by theresistanceA of theload. lThi'sis the'normal operating*Condition.;kv If the vvload `resistance thenvchanges tocause anl-overloa'd the balancev between the field coils will be disturbed andthe` section, another iorm of y i y i 2 l e ybe seeny thatthe systemk shown in 17h15 gul'e may j be adjusted 4manually li'or minimum voltage drop in the tube 'for any normal load 'value and will yautomatically cut oil the load ii `anything hapeither increasedorVdecreasedexcessively. l In this iigure I` have also shown an automatic starting *device 231| Vwill release `-limit the load current. n

V tube.

rbarrier anode hole. K Y l Asomewhat greater magnetic iield the intense path i of glow fromthe barrier anode holejand the path" current will thenbe by the drop in the tubeVl to nearly the normalffull load value. Ivi,- on

thev other hand, "the load,resistancefincreases,` -i thus lowering the load current, the 'tube will bev gin to limit its current and effectively disconnect' the rectierlli troni lthe load. Thecurrent of the buckingileld coil must then Q be reduced to allow load current toilow again. `Thus it'will pens to'disturb thel'oad current/toomuch in 5 eitherv Idirection, 4that is',v if'thexload fcurrent is arc ystarting system using ythe ignition trans- Fig. 5. "utomaticoverload interruption'o! the means ofgoverload relay |59in the D. C; load bucking ileld coil 626.v Thestarting control 22|l which lmay be a conventional direct current mo-l` iliary rectifier 20| the seriesvholding coilv of the Regulation of the vol be obtained by connecting a iield coil in shunt with the load. If desired, this coil may have age more nearly constant;

Fl'g. '17 illustrates `the benavlorogf theatre inthe former-|23 and its ucontrolrelay `Illas shown"` and 'more fully ,describedA in thedescription 'of 20 buckingv rfield'coil Icurrent'is accomplishedl by 4 circuity operating and'breaki'ng thecircuit to the tage 'on the load may also .14o With no magnetic ileld,ror withaweak eld, a drop shapedv relatively intense'glow is'pr'esy ent on` the under or ycathode side of thehole i fthrough the barrier anode, andthe mainbody 'of the tube, between the barrier anode and `mercury pool cathode, iis illled with a moreor lessunii'orm glowsomewhat asillu'stra'tedin Fig. 17A;

If a moderate magnetic fieldis applied the dropv n shaped glow isy stretched out or elongatedfsomer`what'asillustrated 'in Fig. 17B and the yglowy .in

the main bodyofthe tube is reduced yand slightly' concentrated toward the center.`V A still moreinf "tense magnetic ileld elongates the glow still more 4and another region Aof intense glow appears stretching up from the cathode giving an'arc with something like i `a sin'uously "moving hour glass shape, very much like a miniature torr'lado, somef what as illustrated in Fig. 17Cl A still higher iieldr gives a sinuously movin'gintns'ely' lighted are discharge extending all the [way from the barrier anode hole w the catnodesomewnat llike that ll- A lustrated in Fig; 17D. At thefsarne'time an an ode dark space begins to appearfin'and nearthe Forabout 'thesaine or a of glow from the cathode frequently seem to sepa` the vcathanode hole'grows invsi'ze `quickly and exto the'anod only,4 'the"anode"c urrent can be comwwwv 'extinguishe and femmextimi'shed! tinguishesf' the anode :currentff If: there yiscurrentjy 25 rtor startingbox, is providedtogradually apply the neld current to the bucking coil 5 6 and thus graduallyrapply full load kcurrent to the ydirect i t current load. In the case of failure of the aux-1.

and effectively. i l

35 ThyriteVresistors in vseries with it to make the'` field current vary more rapidly with the variation y A y*in load yvoltage'and `thei'eiorehold the' load'volltitingpont yas shown in4 Fig`."14`. 'AlthoughI the l y However, if there is a holding arc current to the cathanode or barrier anode, the anode current usually re-establishes itself and extinguishes itseli' intermittently.

Application of a magnetic field of increasing strength gives a whirling motion to the arc and the gas and vapor near the cathanode hole and along the axis of the arc. This whirling motion, caused by radial components of current. sets up centrifugal forces which lowers the gas and vapor density near and in the cathanode hole. This lowering of the gas and vapor density is visible in its effects through an increase in the free path of ions drawn through the cathanode hole. As a result of the increase in free path of the ions the intensely illuminated glow around the hole is elongated in the manner illustrated in Fig. 17. For quite strong ilelds the pressure along the axis of the whole path of the arc becomes so low that a large proportion of the ions drawn from the cathanode hole travels almost all the way to the cathode before striking a molecule. This indicates that the whirling arc actually does produce a relatively high vacuum along the axis of the tube, in the cathanode hole and in the anode chamber.

The hour glass shape of the arc in Hg. 17C is due to the tendency for the arc to whirl in opposite directions at its two ends. Concentration of arc current at the cathanode hole and at the cathode spot gives radial components of current in opposite directions and therefore opposite rotation of the arc.

The double whirling are of Fig. 17D is also undoubtedly a result of two overlapping oppositely whirling arc paths.

It should be distinctly understood that the present invention is not limited to the precise arrangements and design features shown in the various iigures since these have merely been illustrated for the purpose of setting forth the principles of the present invention and alterations within the scope of the appended claims may be made.

I claim:

1. An arc discharge circuit breaker comprising an anode, an apertured barrier anode and cathode, means for establishing an are between the cathode and the barrier anode, means for establishing a second arc between the cathode and the anode and means responsive to an increase in the second arc current for interrupting said arc.

2. An arc discharge circuit breaker comprising means for establishing an arc discharge in an ionizable medium, means comprising an apertured barrier anode providing a restricted arc discharge path whereby the arc discharge current is interrupted at a predetermined value and a magnetic field parallel to said arc discharge path ion varying said predetermined value.

3. An arc discharge circuit breaker comprising an anode. an apertured barrier anode and a cathode, means for establishing an are between the cathode and the barrier anode, means for establishing a second arc between the cathode and the anode, and magnetic means responsive to an increase in the second arc current for interrupting said arc.

4. An arc discharge switch comprising an anode, an apertured barrier anode and a cathode, means for establishing an arc discharge between the barrier anode and the cathode. means for establishing an are between the cathode and the anode, a source of direct current and load circuit, said second arc connected between said source andsaidloadcircuitandmeanstoa an evacuated casing,

change in resistance of the load circuit for interrupting said arcs.

5. An arc discharge switch comprising an anode, an apertured barrier anode and a cathode, means for establishing an arc between the cathode and the barrier anode, means for establishing an arc between the cathode and the anode, a source of direct current and load circuit, said second arc connected between said source and said load circuit and means for maintaining the second arc current within predetermined limits.

6. An arc discharge switch comprising an apertured first anode, a second anode and a cathode, means for establishing an arc between the cathode and the first anode, means for establishing an arc between the cathode and the second anode through said iirst anode, a source oi direct current and a load circuit, the arc between said cathode and said second anode being interposed between said source and said load circuit and means responsive to a change in the resistance of load circuit for interrupting the arc between said second anode and the cathode.

7. A mercury arc switch comprising a cathode, an anode and an apertured barrier anode within means for establishing an arc between said cathode and said barrier anode, means including a direct current source and a load circuit for establishing an arc between said cathode and said anode through said barrier anode, a magnet coil surrounding said casing and so arranged that its axis is coincident with the arc path and means for energizing said magnet coil whereby said arc is caused to rotate.

8. A mercury arc switch comprising an evacuated casing having therein a cathode and an anode and a barrier anode having a central aperture therein, means for establishing an arc between said cathode and anode through the aperture in said barrier anode, means for establishing an auxiliary arc between the cathode and the barrier anode; a direct current source and a load circuit, the first mentioned arc being in series between said source and said load, a magnet coil surrounding said casing and in co-axial relationship with the hole in the barrier anode, means between the barrier anode and the cathode for spreading the arc and means for energizing said magnet coil whereby a whirlpool rotation is imparted to said arc.

9. A mercury arc switch comprising an evacuated casing having therein a mercury pool cathode,ananodeandabarrieranode havingacentral aperture therein, means for establishing an arc between said cathode and anode through the aperture in said barrier anode, means for establishing an auxiliary arc between the cathode and the barrier anode, a direct current source and a load circuit, the first mentioned arc being in series between said source and said load, a magnet coilsurroundingsaidcasingandinco-axialrelationship with the hole in the barrier anode, means between the barrier anode and the cathode for spreading the arc and means for energizing said magnet coil whereby a whirlpool rotation is imparted to said arc.

10. A mercury are switch comprising an evacuated casing having a mercury pool cathode at oneend,ananodeattheotherendandabarrier anode having an aperture therethrough between the cathode and the anode, means for establishinganauxiliaryarcdischargenomsaidcathode to said barrier anode, means for establishing an are discharge from the cathode to the anode through the aperture in the barrier anode, said aperture being so dinie'iisioiied that the arc chargelcllrlent :cannot exceed e: predetermined the, cathode andthel barrier ianode, `means-:iy for v establishing aesecond arc,between-ithe-..cathode flo .` ing said arc.

and the anodethrough the aperturer in` the-,barrier anode, and .means responsive: to an increase :the second j arc currentvior interrupting seid 12. arc discharge ingL any anode. an ,apertured ban-ier anode and a cathode.-meansior establishingl awarcybetween the cathode andthe barrier,` anodegi-f-means for establishing a fr secondy arc @betweenvthe `cathode and the anode through thefapexture inthe barx'ierr anode, andy magnetic means responsive. tofln increaser` in the second v arc ;,current;for\ interrupt 13. An arcfdischargeswitch comprising ananode. an= aperture'd barrierfanodef-'and atcathode. means `for 'establishing arc discharge between the` cathodey and the barrier anode," means for establishing an arc between thegcathode andthe anode through the aperture in the barrier; anode, a Sourcen! direct current and a load circuitl lsaid second arc being interposed.; between saldi-source andsaid vload circultvvand l*means n responsive to a changefnQ-resistance, of the load circuit for interrupting-said second arc.

14. An arcdischarge switch comprising-elan `anode, an apertured *barriera* anode and av cathode. means for establishingy an arc betweenthe cathode and the barrierfanode,means for establish-k ing an arc betweenthecathode, and the anode through thefeaperture inthe] barrier` anode, a source of direct current vand aV load circuit, said see-ond erebeing interposed between seid source end said ioedeireuit, sam aperture beingsepdimensioned that the second arc current yis tainedfwithinpredetermined limits,v 15. A meruryfkarc switch comprising an ev'acf uatedcasing having therein a cathode, anzanode andra barrier' anode having a central l aperture therein, means ior establishing an arc between said cathode and anode through the aperture in' saidlb'arriery anode, means for establishing an auxiliary arc between the. cathode, and lthe r Ibarg-i rler anode; a magnet coil surrounding saidjcasingj and in'co-axial relationship `with the' hole in the barrier' anodek a direct current source` and a Ioadcircuit, the; first mentioned arc and Vsaid magnet coilfbeing in series' between said'source and said loadywherebysaidflrst mentioned arcl is caused to rotate, theA velocity oi "rotation creasing with increasing curi-enty throughlsaid arc" and said vcoil `-up to acritical value wherethe arc" collapses.y A *l 4 .Y

16.- A' mercury arc switch comprising an evac-y uated casingA havingthereiria cathode and anode and a barrier' anode-having a central aperture therein, means for establishing an arc between said cathode and anode through the `aperture in said barrier anode, meansfio'r establishing an yauxiliary arc between the Vcathodeand 'the bare' rieranode, yar direct current source and a' load said arciscaused to yrotate.\ Y

17. An arc discharge device comprising an o casing having therein an anode at one f-'endseifmereury poolrl cathode 'at the other endf'an'd -tialiiluraiityfoi barriers an'des 'between-@the' cathode trui".apertureIy for" establishing `are discliarge ybetweenl seid-fcathodeand anode.' vmeans for establishiriganf A cfldischa'rge between--the cathode and each`v` fory the barrier-f 'anodes "and meanssii'or "maintainingffeach oi-f said*v barrier flllodet Wpredet'e'r inedpotentialivwithrespect r iizsfAn farc l discharge device comprising an ,once-fend; i a" mercury pool' rcathoc'ie fat the* other yonli-and? :rf-plurality of barrier anodesbetweenfthfe n cathode" and"`anode,'each-barrieranode having a eentrarfeperture; the apertures in *asiel alignme`nt,-l niean'swl'r es'stablishingy an `arc discharge between" 'saidr catltiiie'y and `anode f through the apertures in the @barrier fariodesl means rox' cathod' e' mici` ff 'the barrereneuesf and ymelun" fruiaint'aining eeeiijefI theanodesatia predeterfnued potential withjrespect to r-.the cathode;

evacuated rv'casing' 'having' therein a'icathode at onelend, a control anodelat `the `fotler`end and 'aI plural-ity of ahodes each having a centrala'perf wrecbetlwen Sed cathode .endtfconel amide. .a

2o establishing@ -discnerjge between 'jule source-of direct currentaiii a'losld rcuitQm'eang forgestbllshins v ,an hra twenfthfe said cathode and `-earch oi said`janodes','the"cath ode'and the second apertured ano'defbeing con;

nected infseriesfwith,theldirectcurrent source an arc discharge betweenlthe cathodeand the barrier anode, a source of alternating current connected to rsaid cathode and .anodesv'ior establishing an 'arc I between said cathode `.and each oifsaid'anodes throughthe aperture in the baro-y vrie'r 'anodeya direct currentloutput circuitconnected to said rectinerga magnet coil surround-` saidrcasing and yin axial ralignment with the aperture inthe .barrieranode, said coil connected in series'with the,v output circuit whereby ari-increase inthedirect currentoutput above ya pre-y determinedvalue will extinguish the arc through mezbrrier'wde. 1' i i .f

. 21', mercury arc switch comprising anuevacuated casing having' therein a cathode (at, one end.an anode at rthe other endand a barrier anode having a. central aperture ltherein between said anoiie said cathode, :means for v.estab-v lishlngfan; arc ,between saicl` cathode and said anode through the aperture in saidbarrier anode,

means 'for establishing anrhauxiliary arc dischargel beizyvgu'ax;,thek cathode andl the barrier anode, a plurality oil-magnet coils surrounding said casing and inV cofaxial relationship-with the aperture in the barrier anode, a. direct current sourceiand aloadcircruit, the rst mentioned arc andoney of `the ymagnet -coils being Aconnected in` seriesbe#v tween'. said `source and said ,.ioadfwhereby said ilrst,r mentioned arc is given J a whirlpool frotationf limiting the arc current to apredetermined value,

means for energizing the other of said magnet coils to an opposing sense to that of the ilrst whereby the limiting efi'ect of the rst is removed, and means for de-energizing said second s mentioned coil when the current drawn by the load exceeds a predetermined value.

22. A mercury arc switch comprising an evacuated casing having therein a cathode at one end, an anode at the other end and a barrier anode having a central aperture therein between said anode and said cathode, means for establishing an arc between said cathode and said anode through the aperture in said barrier anode. means for establishing an auxiliary arc discharge between the cathode and the barrier anode, a plurality of magnet coils surrounding said casing and in co-axial relationship with the aperture in the barrier anode, a direct current source and a load circuit, the nrst mentioned arc and one of the magnet coils being connected in series between said source and said load whereby said first mentioned arc is given a whirlpool rotation limiting the arc current to a predetermined value, and means for energizing the other of of the rst whereby the limiting effect of the nrst is removed.

23. A mercury arc discharge device comprising a base plate having a depression containing a mercury pool, a barrier anode plate having a central aperture, an insulating cylindrical wall member separating said base plate and said barrier anode plate, means for clamping said plates together forming a cathode chamber, and an anode and an anode supporting cup clamped over the aperture in the barrier anode forming an anode chamber, an insulating ring within the depression in the base plate for retaining the cathode spot on the mercury surface and an n arc deilectng plate mounted in said cathode chamber in alignment with the aperture in the barrier anode.

24. A mercury arc discharge device comprising a base plate having a depression containing av mercury pool, a barrier anode plate having a central aperture, an insulating cylindrical wall member separating said base plate and said barrier anode plate forming a cathode chamber. means for clamping said plates together, an

I0 anode and an anode supporting cup clamped over the aperture in the barrier anode forming an anode chamber, an insulating ring within the depression in the base plate for retaining the cathode spot on the mercury surface, an arc de- 55 fleeting plate mounted in said cathode chamber in alignment with the aperture in the barrier anode, the surface of the arc deiiecting plate and the barrier anode being covered with an insulating enamel.

25. A mercury arc discharge device comprising a. base plate having a depression containing a mercury pool, a barrier anode plate having a central aperture, an insulating cylindrical wall member separating said base plate and said bar- 65 rier anode plate forming a cathode chamber, means for clamping said plates together, an anode and an anode supporting cup clamped over the aperture in the barrier anode forming an anode chamber, an insulating ring within the 70 depression in the base plate for retaining the cathode spot on the mercury surface, an arc deflecting plate mounted in said cathode chamber in alignment with the aperture in the barrier anode, the surface of `the arc deiiecting 75 plate and the barrier anode being covered with said magnet coils to an opposing sense to that an insulating enamel, and a high resistance arc starter point supported near the mercury pool surface by an insulated connection through the base plate.

26. A mercury arc discharge device comprising a base plate having a depression containing a mercury pool, a barrier anode plate having a central aperture. an insulating cylindrical wall member separating said base plate and said barriet anode plate forming a cathode chamber, means for clamping said plates together, an anode and an anode supporting cup clamped over the aperture in the barrier anode forming an anode chamber, an insulating ring within the depression in the base plate for retaining the cathode spot on the mercury surface, an arc deiiecting plate mounted in said cathode chamber in alignment with the aperture in the barrier anode, the surface of the arc defiecting plate and the barrier anode being covered with an insulating enamel, and a high resistance arc starter point supported near the mercury pool surface by an insulated connection through the base plate, the barrier anode plate having cooling passages surrounding the central aperture thereof.

27. A mercury arc discharge device comprising a base plate having a depression containing a mercury pool, a barrier anode supporting plate having a plurality of apertures therethrough, an insulating cylindrical wall member separating said supporting plate and said base plate forming a cathode chamber, means for clamping said plates together, an apertured barrier anode in each aperture in the barrier anode supporting plate, an anode and an anode supporting cup clamped over the aperture in each barrier anode forming anode chambers, an insulating ring within the depression in the base plate for retaining the cathode spot on the mercury surface and a high resistance arc starter point supported near the mercury pool surface by an insulated connection through the base plate.

28. A mercury arc discharge device comprising a base plate having a depression containing a mercury pool, a barrier anode supporting plate having a plurality of apertures therethrough, an insulating cylindrical wall member separating said supporting plate and said base plate forming a cathode chamber, means for clamping said plates together, an apertured barrier anode in each aperture in the barrier supporting plate, an anode and an anode supporting cup clamped over the aperture in each barrier anode forming anode chambers, an insulating ring within the depression in the base plate for retaining the cathode spot on the mercury surface and a high resistance arc starter point supported near the mercury pool surface by an insulated connection through the kms@ plate, each barrier anode having cooling passages surrounding the central aperture thereof.

29. An arc discharge device comprising a cathode, an anode and an apertured barrier anode within an evacuated casing, means for establishing an arc between said cathode and said barrier anode, means including a direct current source and a load circuit for tablishing an arc between said cathode and said anode through said barrier anode, a magnet coil surrounding said casing and so arranged that its axis is coincident with the arc path, means for energizing said magnet coil whereby said arc is caused to rotate and means within said casing for concenan anode and a barrier anode having acentral aperture therein, means for establishing an arc between said cathode and said anode through the aperture in in said barrier anode, means vfor establishing an auxiliary arc between said cathode and said barrier anode; a direct current source and a load circuit, the first mentioned arc being in series between said source and said load, a magnet coil surrounding said casing and in coaxial relationship with the hole in said barrier anode, a ferromagnetic arc deflecting plate between said barrier anode and said cathode for spreading the arc and means for energizing said magnet coil whereby a whirlpool rotation is imparted to said arc, said arc deiiecting plate acting to concentrate the field from said coil.

31. An arc discharge circuit breaker comprising kvmeans for establishing an arc discharge in an ionizable medium, a barrier anode having an aperture therein and so arranged that said arc discharge must pass through said aperture, the dimensions of said aperture being so chosen that the path of said arc discharge is restricted whereby the arc discharge current is interrupted at a predetermined value and means for establishing a variable magnetic ileld parallel to the axis of said `aperture whereby said predetermined value may be varied.

32. An arc discharge circuit breaker comprising means for establishing an arc discharge in an ionizable medium, a barrier anode having an aperture therein and so arranged that said arc discharge must pass through said aperture, the dimensions of said aperture being so chosen that the path of said arc discharge is restricted whereby the arc discharge current cannot exceed a predetermined value, and means for establishing an auxiliary arc discharge in said medium for maintaining said medium in an ionized condition.

CLARENCE W. HANSELL. 

